I have no idea what kind of JB4 I have lol...I doubt its a G5 though cause I've had it for a year and a half....so is this compatible with it? Or do I need the G4 as well in order to do this upgrade?

You should be good! All you need to do is swap your board with this one and you will have all the features of G5 and isolated boost control. Only thing is on the older JB4 harnesses you may have to switch a pin or two. Email terry.